Tunnel waterproofing method

ABSTRACT

To provide a waterproofing construction method with which excellent waterproofing capacity can be assured. A tunnel waterproofing method characterized in that a primary spray cement concrete is sprayed on the excavation surface of the tunnel, after which a waterproofing sheet having adhesiveness with a secondary coating cement concrete is installed on said primary spray cement concrete surface and a secondary coating cement concrete is established on said waterproofing sheet surface. A buffer-water conducting layer may also be established on said primary spray cement concrete surface and a multilayer waterproofing sheet having adhesiveness with the applied cement concete may also be installed as a waterproofing sheet.

DETAILED DESCRIPTION OF THE INVENTION

[0001] 1. Technological Field of the Invention

[0002] This invention relates to a waterproofing method for tunnels.

[0003] In this invention, paste, mortar and concrete are used as generalterms to refer to cement concrete.

[0004] 2. Prior Art

[0005] The principal tunnel construction method in Japan at present isthe NATM method. The NATM construction method is a method in whichprimary coating is performed by means of spray mortar or spray concreteimmediately after excavation of the tunnel to prevent falling of rockand water leakage in the excavation region, after which a secondarycoating concrete is applied to stabilize the tunnel by maintainingtunnel strength. At this time, a waterproofing sheet is installed forthe purpose of waterproofing and insulation between the primary coatingconcrete and the secondary coating concrete so that leakage of waterinto the tunnel can be prevented and so that cracks due to binding ofthe secondary coating concrete to earth mounds or movement of earthmounds can be prevented. Most recently, tunnel excavation has beenperformed by tunnel boring machines (TBM construction method) andwaterproofing sheets are installed for the same objectives.

[0006] Further, because the width of the sheet is narrow, being 1 to 2m, there are the problems that it takes great effort and trouble and itis uneconomical when the ends of the waterproofing sheets are overlaidon each other and joined by welding.

[0007] There is the further problem that water infiltrates between thewaterproofing sheets and the secondary coating concrete due to damage ofthe waterproofing sheet functionally by poorly welded components and byirregularities in the excavation surface so that waterproofing capacityis not obtained.

[0008] [Problems the Invention is Intended to Solve]

[0009] When the thickness of the waterproofing sheets is increased inorder to prevent damage to the waterproofing sheets, there are theproblems that welding of the ends of the waterproofing sheets becomesdifficult and that the mass of the waterproofing sheets is increased,with the result that actual execution characteristics become evenpoorer.

[0010] The inventors conducted various studies of the aforementionedproblems. As a result, they perfected this invention by discovering atunnel waterproofing construction method whereby a waterproofing sheetthat is adhesive to the secondary coating cement concrete is installedon the primary spray cement concrete surface before installing thesecondary coating cement concrete, and, in which, by making it into asingle entity with the secondary coating cement concrete, infiltrationof water between the waterproofing sheet and the secondary coatingconcrete because of poor weld sites and damage of the ends of thewaterproofing sheets is prevented, leakage of water is prevented evenwhen cracks are generated in the secondary coating cement concrete andwaterproofing capacity can be greatly increased.

[0011] [Means for Solving the Problems]

[0012] Specifically, this invention is a tunnel waterproofing methodcharacterized in that a primary spray cement concrete is sprayed on theexcavation surface of the tunnel, after which a secondary coating cementconcrete and a waterproofing sheet having adhesiveness are installed onsaid primary spray cement concrete surface such that the secondarycoating cement concrete is established on said waterproofing sheetsurface, [or] a tunnel waterproofing method characterized in that aprimary spray cement concrete is sprayed on the excavation surface ofthe tunnel, after which a buffer-water conducting layer is establishedin said primary spray cement concrete surface, a secondary coatingcement concrete and a waterproofing sheet having adhesiveness areinstalled on said secondary coating cement concrete such that thesecondary coating cement concrete is established on said waterproofingsheet surface; and a tunnel waterproofing method further characterizedin that the waterproofing sheet is a multilayer waterproofing sheet thathas a layer that has adhesiveness with the installed secondary coatingcement concrete.

[0013] [Mode of Execution of the Invention]

[0014] We shall now describe this invention in detail.

[0015] This invention is a construction method in which thewaterproofing sheet and the tunnel are made into a single entity byspraying, preferably, a fast-drying cement concrete onto the excavatedtunnel surface, after which a waterproofing sheet that is adhesive withthe secondary coating cement concrete is installed. This waterproofingsheet allows for follow-up of cracking of cement concrete due to dryingand contraction of the secondary coating cement concrete and of earthmounds after completion. By making the cement concrete and thewaterproofing sheet into a single entity, contact with water occurs onlyin sites that are damaged even if damage to the waterproofing sheetsoccurs. For this reason, leakage of water does not occur as long ascracks do not develop in the secondary coating concrete in the region ofthe sheet damage. Therefore, water leakage is greatly decreased andexcellent waterproofing capacity is obtained. Further, water leakagedoes not occur as with conventional waterproofing sheets as a result ofwater infiltrating between the waterproofing sheet and the secondarycoating cement concrete, of impairment of the waterproofing capacity ofthe tunnel as a whole, and of cracks in the secondary coating cementconcrete. Moreover, because a waterproofing sheet that is made into asingle entity with the secondary coating cement concrete prevents waterleakage with good follow-up capacity and without damage occurring evenwhen cracks are generated in the tunnel itself, waterproofing capacityis increased to a great extent by comparison to conventionalwaterproofing construction methods.

[0016] Examples of waterproofing sheets that are adhesive with secondarycoating cement concrete include uncrosslinked rubber sheets such asisoprene rubber and natural rubber.

[0017] The waterproofing sheet that is adhesive with the secondarycoating cement concrete may also contain antioxidants, ultravioletradiation absorbents and tackiness-decreasing agents.

[0018] In this invention, it is desirable to laminate the layer havingadhesiveness with the secondary cement concrete with a polymeric sheetfrom the standpoint of increasing the insulation effect with thesecondary coating cement concrete if it has been bound with the earthmound. When a layer that is adhesive with the secondary coating cementconcrete and a multilayer waterproofing sheet that is laminated with apolymeric sheet are used, they are installed so that the primary spraycement concrete surface side and the polymeric sheet are in contact andthe secondary coating cement concrete is installed on the waterproofingsheet surface side that is adhesive with the secondary coating cementconcrete.

[0019] Examples of the material of the polymeric sheet can includehigh-density polyethylene, low-density polyethylene, copolymers ofethylene vinyl acetate (EVA) and polypropylene. Of these, high-densitypolypropylene is preferable from the standpoint of insulation effect,strength, crack follow-up capacity and price.

[0020] In this invention, a buffer-water conducting layer may beestablished before installing the waterproofing sheet that is adhesivewith the secondary coating cement concrete for the purpose of increasingthe insulation effect, decreasing water pressure in sites in which thereis a great deal of groundwater and increasing the waterproofing effect.Examples of buffer-waterproofing layers can include layers that areformed by spraying a fibrous substance such as pulp nonwoven fabrics offibers such as polyester fibers and polypropylene and plates orirregular shapes.

[0021] The waterproofing construction method can be used in the beddingportion of the tunnel and displays great effectiveness in preventingwater leakage from the bedding component.

[0022] There are no particular limitations on the method of affixing thewaterproofing sheet, nonwoven fabric and plates of irregular shape tothe primary spray cement concrete surface and adhesive agents and rivetsmay be used.

[0023] After the waterproofing sheet that is adhesive to the secondarycoating cement concrete has been installed in this way, the secondarycoating cement concrete is applied and construction is completed.

EXAMPLES

[0024] We shall now describe this invention in detail on the basis ofexamples.

Example 1

[0025] A U-shaped simulation tunnel having openings of 4 m, a height of3.5 m and a length of 3 m was made. Irregularities of the tunnel earthmound surface were presumed in the simulation tunnel and fifteenconcrete blocks of 15 cm in width, 20 cm in height and 20 cm in lengthwere installed at suitable intervals to form an irregular surface.

[0026] Fast-drying mortar was used as the primary spray mortar and wassprayed so that the fast-drying mortar was 10 cm in thickness.

[0027] After spraying, a multilayer waterproofing sheet havingadhesiveness to the secondary coating concrete (brand name, “Preprufe300,” manufactured by the Grace Construction Products Company of theUnited States; a two-layer sheet comprised of two layers, a layer havingadhesiveness to concrete and a polyethylene layer; 2.7 mm in thickness)was affixed by riveting to the primary spray mortar surface. Followingthat, the secondary coating concrete was applied to a thickness of 30cm. To simulate damage to the multilayer waterproofing sheet, cuts weremade in a part of it.

[0028] Twenty-eight days after the secondary coating concrete wasestablished, a test sample was cut out by boring and adhesiveness withthe concrete was checked. The secondary coating concrete and thewaterproofing sheet were in good contact and were a single entity. Thepeeling strength of the secondary coating concrete and the waterproofingsheet was greater than 0.9 N/mm.

[0029] A single entity with the secondary coating concrete was also wellmaintained in the region of the cut, with the cut in the concrete beingin a linear pattern of less than 2 mm. A static water pressure of 60 mwas applied in the gap between the primary spray concrete and themultilayer waterproofing sheet. However, water did not enter into thegap between the multilayer waterproofing sheet and the secondary coatingconcrete, with good waterproofing capacity being shown.

[0030] Because the multilayer waterproofing sheet that was used hadadhesiveness, the multilayer waterproofing sheets could be adhered toeach other satisfactorily simply by superimposing the ends of themultilayer waterproofing sheets on each other. For this reason,execution capacity was extremely good and an excellent value of 1.7 N/mmwas obtained for adhesive strength of the superimposed parts.

[0031] To simulate cracks in the tunnel, stress was applied to thesecondary coating concrete and cracks were made. No abnormalities wereseen in the multilayer waterproofing sheet.

[0032] The test methods for the various physical properties were asfollows.

[0033] Adhesive strength with the concrete: In accordance with ASTM D903 (90 degree peeling strength). Adhesive strength of superimposedportions: In accordance with ASTM D 1876 (Determinations in the case inwhich multilayer waterproofing sheets are superimposed).

Example 2

[0034] The same procedure was carried out as in Example 1 except thatthe multilayer waterproofing sheet having adhesiveness with thesecondary coating concrete that was used was a product of the brand name“Santacket* Sheet” (isoprene rubber waterproofing sheet, a nonwovenfabric lined product, manufactured by Hayakawa Rubber).

[0035] Twenty-eight days after the secondary coating concrete wasestablished, a test sample was cut out by boring and adhesiveness withthe concrete was checked. The secondary coating concrete and thewaterproofing sheet were in good contact and were a single entity.

[0036] However, it was more difficult to join the ends of the multilayerwaterproofing sheets than in Example 1 and workability was also somewhatdifficult.

[0037] Comparative Example 1

[0038] The same procedure was carried out as in Example 1 except that awaterproofing sheet made of EVA (which did not have adhesiveness withthe secondary coating concrete) was used instead of a multilayerwaterproofing sheet having adhesiveness with the secondary coatingconcrete.

[0039] When pressure corresponding to 30 m of static water pressure wasapplied between the primary spray mortar and waterproofing sheet, it wasfound from the cracks in which damage was presumed that a large quantityof water entered into the gap between the waterproofing sheet and thesecondary coating concrete and that properties of a waterproofing sheetwere not obtained.

[0040] [Effect of the Invention]

[0041] By making the secondary coating cement concrete and thewaterproofing sheets into a single entity using the waterproofing sheetsof this invention having adhesiveness with the secondary coating cementconcrete, water does not infiltrate between the gap between thewaterproofing sheets and the secondary coating concrete and excellentwaterproofing capacity can be assured even if a part of thewaterproofing sheets is damaged.

[0042] Further, the crack follow-up of the waterproofing sheets of thisinvention is good, the waterproofing sheets are not damaged andexcellent waterproofing capacity can be assured even if cracks developin the secondary coating cement concrete. Even if by any chance thecrack width is large and damage of the waterproofing sheet occurs,because the other portions of the waterproofing sheet are a singleentity with the secondary coating cement, water does not infiltrate intothe gap between the waterproofing sheets and the secondary coatingconcrete; -therefore, the industrial benefits are extremely great.

1. A tunnel waterproofing method characterized in that a primary spraycement concrete is sprayed on the excavation surface of the tunnel,after which a waterproofing sheet having adhesiveness with a secondarycoating cement concrete is installed on said primary spray cementconcrete surface and a secondary coating cement concrete is establishedon said waterproofing sheet surface:
 2. A tunnel waterproofing methodcharacterized in that a primary spray cement concrete is sprayed on theexcavation surface of the tunnel, after which a buffer-water conductinglayer is established in said primary spray cement concrete surface, awaterproofing sheet having adhesiveness with a secondary coating cementconcrete is installed on said secondary coating cement concrete and asecondary coating cement concrete is established on said waterproofingsheet surface.
 3. A tunnel waterproofing method as described in claims 1and 2, further characterized in that the waterproofing sheet is amultilayer waterproofing sheet that has a layer that has adhesivenesswith the installed secondary coating cement concrete.